1. Field of the Invention
The present invention relates to a method of manufacturing a piezoelectric actuator including a piezoelectric device constituted of a lower electrode, a piezoelectric body and an upper electrode arranged on a diaphragm, a liquid ejection head including this piezoelectric actuator, and an image forming apparatus including this liquid ejection head.
2. Description of the Related Art
In general, an inkjet recording apparatus performs recording by ejecting and depositing droplets of ink onto a recording medium from nozzles of a recording head (inkjet head), and such a method is able to record images of high resolution and high quality, with little noise during the recording operation and low running costs, and therefore is widely used in a variety of fields. As an ink ejection method, it is desirable to use a method which ejects an ink droplet from a nozzle connected to a pressure chamber by pressing ink inside the pressure chamber by using the displacement of a piezoelectric element, for example, to move the wall surface of the pressure chamber.
It is known that if a piezoelectric element is driven for a long time, then the displacement properties of the element decline. As a method for restoring the decline of the piezoelectric properties of a piezoelectric element due to such use, Japanese Patent Application Publication No. 06-342946, for instance, proposes a method whereby the piezoelectric element is subjected to an annealing process at a temperature not lower than the Curie point of the piezoelectric material.
However, in the method described in Japanese Patent Application Publication No. 06-342946, although it is possible to eliminate decline in the displacement properties of the piezoelectric element by carrying out the annealing of the piezoelectric element after the element has been driven for a long period of time, since the restoration process is ultimately required after decline in displacement has occurred, then there is a problem in that the piezoelectric element is driven in a state of degraded displacement properties over a long period of time.
In particular, in a process of manufacturing an inkjet head, when the piezoelectric body is subjected to polishing and heat treatment, there is marked decline in the displacement properties of the piezoelectric element and this gives rise to degradation in the image due to the occurrence of fluctuations in the ink ejection properties.